After attending St Michael's male academy in Chatham, James M. Troy went to work, at age sixteen, with George Brown of Newcastle to learn the construction trade. He later took an architectural course in Toronto and returned to start his own contracting business. By 1873 he was a reputable builder, and for more than thirty years he took contracts for the construction of homes, schools, churches, and other structures. In 1879 he was the contractor for the William Watt house (now the 'Old Manse') in Newcastle. His workmanship, and that of his subcontractors, on this building was said to be as good as any to be found in the province. He erected the first Newcastle curling rink in 1882. In 1893 he renovated the Methodist church in Newcastle and built an eighty-two-foot spire for it. In 1893 he also had the contract for the Methodist church at Derby. In 1899 he built a new Adams House in Chatham for Thomas Flanagan after the former one burned down. Between 1900 and 1902 he erected the splendid new St John's Presbyterian Church in Chatham from plans drawn by a Halifax architectural firm. He was the contractor for the Bethel Presbyterian Church at Millbank, which was opened on 31 December 1905, and the designer of St Stephen's Presbyterian Church at Black River, which was built in 1906 by the contractor James S. Hill.

In 1907 Troy, who was then past sixty, was appointed postmaster at Newcastle, as successor to William P. Harriman. In 1913 he was elected president of the New Brunswick Postmasters' Association. It was stated in 1928, when he was eighty-two, that he was at work every day before 6:00 a.m. and always stayed until the last letter was stamped. He continued in office until his death in 1935, at age eighty-nine.

In 1893 Troy was worshipful master of Northumberland Lodge, and he was a member of that Masonic body for more than sixty years. He was also a longtime member of the Newcastle Sons of Temperance. He was from a Catholic family but became a Presbyterian at the time of his marriage. In 1907 he was one of twelve trustees of St James Church. During church union in 1925-26 he was chairman of the trustees, and he was the first chairman of the board of stewards of St James and St John United Church. He served a term as president of the County Liberal Association and sometimes spoke in political campaigns.

Troy and his wife, Phylinda Vaughan, had three daughters and four sons. Their daughter M. Edith Troy, the wife of Charles Sargeant Jr, was a graduate of Mount Allison Ladies' College and a music teacher and organist in Newcastle. Their daughter Charlotte Troy was the wife of A. Ernest G. McKenzie. Their son James G. Troy was inspector of customs at Newcastle in 1923-24 and later town registrar and provincial government inspector. The youngest of their four sons was John H. Troy.

James M. Troy's brother John Troy was the postmaster at Douglastown for thirty years, and his brother Patrick B. Troy was an outstanding architect and builder, first at Chatham and then at Dalhousie, N.B., erecting some of the leading public and commercial buildings at Dalhousie and Campbellton and along the Gaspé coast of Quebec.